The role of cytosolic sialidase in developing enamel organs.

我们对大鼠磨牙胚进行了原位杂交、免疫细胞化学和凝集细胞化学研究，得到了如下结果。(1)原位杂交研究：胞质唾液酸酶mrna水平随细胞分化变化较大。在口腔上皮、外、内牙釉质上皮和牙乳头中含量较高。在星状网和口腔上皮与外牙釉质上皮之间的移行细胞中极低或几乎检测不到，提示其移行急剧下降。虽然在牙乳头中mRNA表达的整体图像较高，但间充质细胞表达的mRNA水平彼此不同。(2)免疫细胞化学研究：口腔上皮、牙釉质器官和牙乳头各细胞均表达高水平的胞质唾液酸酶蛋白。酶蛋白定位于每个细胞的细胞质、核质和线粒体基质。它的定位模式与大鼠的骨骼细胞和肌肉细胞非常相似，这表明它在许多类型的细胞中普遍存在。从免疫金颗粒的数量来看，在细胞分化过程中，酶蛋白的含量变化不大。从这个角度来看，酶蛋白的表达与mRNA的表达不同。(3)凝集素-细胞化学研究：牙胚细胞表面和细胞外基质中存在大量凝集素（Limax flavus）结合位点。但在细胞质中数量较少。我们检查了这些结合位点中的一小部分是否有意义。抑制糖可以有效地将结合位点降低约一半的水平，表明存在假定的细胞质唾液糖缀合物。非特异性凝集素与细胞质结合的可能性仍然需要通过进行补充实验来排除，其中结合位点预计会在被细胞质唾液酸酶消化的组织切片中减少。少

We obtained following results in in situ hybridization, immunocytochemical, and lectincytochemical studies of rat molar tooth germs.(1) in situ hybridization study : The level of cytosolic sialidase-mRNAs changed largely with cell differentiation. It was high in the oral epithelium, outer and inner enamel epithelium, and dental papilla. It was very low or barely detectable in the stellate reticulum and transitional cells between the oral epithelium and the outer enamel epithelium, suggesting its steep drop in transition. Although the overall image of the mRNA expression was high in dental papilla, the mesenchymal cells expressed different levels of the mRNAs from each other.(2) immunocytochemical study : Every cell expressed high levels of cytosolic sialidase-protein in the oral epithelium, enamel organ and dental papilla. The enzyme protein was localized in the cytoplasm, nucleoplasm and mitochondrial matrix of each cell. Its Iocalization pattern was very similar to that in skeletal m … More uscle cells of rats, suggesting it being ubiquitous in many types of cells. Based on the number of immunogold particles, the amount of the enzyme protein did not largely change in cells during the course of cell differentiation. In this point of view the expression of the enzyme protein was different from that of the mRNA.(3) lectin-cytochemical study : Lectin (Limax flavus)-binding sites were numerous on the cell surface and in the extracellular matrix of tooth germs. However the number of them were small in the cytoplasm. We examined whether a small number of those binding sites were meaningful or not. An inhibitory sugar was effective in decreasing the binding sites at about a half level, indicating the presence of putative cytoplasmic sialoglycoconjugates. The possibility of non-specific lectin binding to the cytoplasm remains to be excluded by conducting a supplementary experiment in which the binding sites are expected to decrease in tissue sections digested by cytosolic sialidase. Less